MAC and RLC architecture and procedures to enable reception from multiple transmission points

ABSTRACT

A method for use in a wireless transmit receive unit (WTRU) for two-stage reordering of received protocol data units (PDUs). The method comprising receiving PDUs from Node-Bs, wherein each of the received PDUs has a transmission sequence number (TSN), reordering the received PDUs from Node-Bs using the TSN in a MAC layer in different reordering queues, delivering the received PDUs from reordering queues to one logical channel in the RLC layer, reordering the received PDUs in the RLC layer based on a sequence number (SN), starting a timer when at least a RLC PDU is missing based on SN of the RLC PDU, and transmitting a status report indicating a missing RLC PDU based on SN of the RLC PDU if the timer expires, wherein transmission of the status report is delayed if a RLC PDU is missing based on SN of the RLC PDU and the timer is running.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional application No.61/388,976 filed Oct. 1, 2010, the contents of which is herebyincorporated by reference herein.

BACKGROUND

In Release-7 of Universal Mobile Telecommunications System (UMTS), theSingle Cell Downlink Machine Input Machine Output (SC-MIMO) feature wasintroduced. SC-MIMO allows a Node-B to transmit two transport blocks toa single wireless transmit/receive unit (WTRU) from the same sector on apair of transmit antennas improving data rates at high geometries andproviding a beam forming advantage to the WTRU in low geometryconditions.

In Release-8 and Release-9 of UMTS, the Dual Cell High Speed DownlinkPacket Access (DC-HSDPA) and Dual Band DC-HSDPA features wereintroduced. Both these features allow the Node-B to serve one or moreusers by simultaneous operation of HSDPA on two different frequencychannels in the same sector, improving experience across the entirecell. The common part of these features is that they allow forsimultaneous downlink reception of two independent transport blocks atthe WTRU, where the transport blocks are transmitted on the High SpeedDownlink Shared Channel (HS-DSCH) by a single Node-B sector.

Another technique that is based on the simultaneous reception of two ormore transport blocks from different cells in the same or differentfrequency is multipoint operation. Multipoint operation consists intransmitting two independent transport blocks to the WTRU, wherein thetransport blocks are transmitted from different Node-B sectors or cellson the same frequency or different frequency and geographicallyseparated points. This may be seen as an extension of the DC-HSDPAfeature on geographically separated cells on the same or differentfrequencies.

Multipoint transmissions may operate with two cells located on twodifferent Node-Bs or in two different sites, referred to hereafter asinter-site mutilflow operation, and an Radio Network Controller (RNC)will split data between two Node-Bs. Each Node-B may then perform MACand PHY layer operations, such as segmentation and TSN generation on thepackets before transmission to the WTRU. Existing MAC and PHY layerprocedures at the WTRU will not be able to process and reconstructpackets in sequence since they are originating from two Node-Bs. The MACDC-HSDPA architecture in the WTRU is not designed to receive data fromdifferent sites. Additionally, reception from different sites mayincrease and introduce the possibility of out-of-order reception,causing potential data dropping in the MAC-ehs entities and prematureRLC status reporting in the RLC entities. Methods to allow inter-siteoperation and reordering in several layers are required.

SUMMARY

A method for use in a wireless transmit receive unit (WTRU) fortwo-stage reordering of received protocol data units (PDUs). The methodcomprises receiving PDUs from a plurality of Node-Bs, wherein each ofthe received PDUs has a transmission sequence number (TSN), reorderingthe received PDUs from each of the plurality of Node-Bs using the TSN ina MAC layer in different reordering queues, delivering the received PDUsfrom a plurality of reordering queues to one logical channel in the RLClayer, reordering the received PDUs in the RLC layer based on a sequencenumber (SN), starting a timer when at least a RLC PDU is missing basedon SN of the RLC PDU, and transmitting a status report indicating amissing RLC PDU based on SN of the RLC PDU on a condition that the timerexpires, wherein transmission of the status report is delayed on acondition that a RLC PDU is missing based on SN of the RLC PDU and thetimer is running.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawingswherein:

FIG. 1A is a system diagram of an example communications system in whichone or more disclosed embodiments may be implemented;

FIG. 1B is a system diagram of an example wireless transmit/receive unit(WTRU) that may be used within the communications system illustrated inFIG. 1A;

FIG. 1C is a system diagram of an example radio access network and anexample core network that may be used within the communications systemillustrated in FIG. 1A;

FIG. 2 shows an example of a MAC architecture for a WTRU havingduplicate MAC-ehs entities;

FIG. 3 shows an example MAC-ehs entity and two sets of reordering queueson the WTRU side where each set of reordering queues includes twoqueues;

FIG. 4 shows an example of a MAC architecture for a WTRU havingduplicate MAC-ehs entities and a MAC-sf entity;

FIG. 5 shows an example of a global MAC-ehs entity in a WTRU having twoglobal reordering sub-entities;

FIG. 6 shows an example of a MAC-sf entity on the UTRAN side;

FIG. 7 shows an example of a MAC-sf entity on the WTRU side;

FIG. 8 shows an example of a MAC-sf entity and duplicated MAC-ehsentities on the WTRU side;

FIG. 9 shows an example MAC-sf PDU;

FIGS. 10A and 10B are a flow diagram that shows an alternativeembodiment where only one Tsf timer is used at a given time;

FIGS. 11A and 11B are a flow diagram that shows an alternativeembodiment where one timer Tsf is used per missing PDU;

FIGS. 12A and 12B are a flow diagram that shows an alternativeembodiment where one timer is used per missing sequence number; and

FIGS. 13A and 13B are a flow diagram that shows the RLC behavior.

DETAILED DESCRIPTION

FIG. 1A is a diagram of an example communications system 100 in whichone or more disclosed embodiments may be implemented. The communicationssystem 100 may be a multiple access system that provides content, suchas voice, data, video, messaging, broadcast, etc., to multiple wirelessusers. The communications system 100 may enable multiple wireless usersto access such content through the sharing of system resources,including wireless bandwidth. For example, the communications systems100 may employ one or more channel access methods, such as code divisionmultiple access (CDMA), time division multiple access (TDMA), frequencydivision multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrierFDMA (SC-FDMA), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, 102 d, a radioaccess network (RAN) 104, a core network 106, a public switchedtelephone network (PSTN) 108, the Internet 110, and other networks 112,though it will be appreciated that the disclosed embodiments contemplateany number of WTRUs, base stations, networks, and/or network elements.Each of the WTRUs 102 a, 102 b, 102 c, 102 d may be any type of deviceconfigured to operate and/or communicate in a wireless environment. Byway of example, the WTRUs 102 a, 102 b, 102 c, 102 d may be configuredto transmit and/or receive wireless signals and may include userequipment (UE), a mobile station, a fixed or mobile subscriber unit, apager, a cellular telephone, a personal digital assistant (PDA), asmartphone, a laptop, a netbook, a personal computer, a wireless sensor,consumer electronics, and the like.

The communications systems 100 may also include a base station 114 a anda base station 114 b. Each of the base stations 114 a, 114 b may be anytype of device configured to wirelessly interface with at least one ofthe WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to one or morecommunication networks, such as the core network 106, the Internet 110,and/or the networks 112. By way of example, the base stations 114 a, 114b may be a base transceiver station (BTS), a Node-B, an eNode B, a HomeNode B, a Home eNode B, a site controller, an access point (AP), awireless router, and the like. While the base stations 114 a, 114 b areeach depicted as a single element, it will be appreciated that the basestations 114 a, 114 b may include any number of interconnected basestations and/or network elements.

The base station 114 a may be part of the RAN 104, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, etc. The base station 114 a and/or the base station 114 b may beconfigured to transmit and/or receive wireless signals within aparticular geographic region, which may be referred to as a cell (notshown). The cell may further be divided into cell sectors. For example,the cell associated with the base station 114 a may be divided intothree sectors. Thus, in one embodiment, the base station 114 a mayinclude three transceivers, i.e., one for each sector of the cell. Inanother embodiment, the base station 114 a may employ multiple-inputmultiple output (MIMO) technology and, therefore, may utilize multipletransceivers for each sector of the cell.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, infrared (IR), ultraviolet (UV), visible light, etc.). Theair interface 116 may be established using any suitable radio accesstechnology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104 and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 116 using wideband CDMA (WCDMA). WCDMAmay include communication protocols such as High-Speed Packet Access(HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed DownlinkPacket Access (HSDPA) and/or High-Speed Uplink Packet Access (HSUPA).

In another embodiment, the base station 114 a and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Evolved UMTSTerrestrial Radio Access (E-UTRA), which may establish the air interface116 using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.16 (i.e.,Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000,CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), InterimStandard 95 (IS-95), Interim Standard 856 (IS-856), Global System forMobile communications (GSM), Enhanced Data rates for GSM Evolution(EDGE), GSM EDGE (GERAN), and the like.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, and the like. In oneembodiment, the base station 114 b and the WTRUs 102 c, 102 d mayimplement a radio technology such as IEEE 802.11 to establish a wirelesslocal area network (WLAN). In another embodiment, the base station 114 band the WTRUs 102 c, 102 d may implement a radio technology such as IEEE802.15 to establish a wireless personal area network (WPAN). In yetanother embodiment, the base station 114 b and the WTRUs 102 c, 102 dmay utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, etc.) to establish a picocell or femtocell. As shown in FIG. 1A,the base station 114 b may have a direct connection to the Internet 110.Thus, the base station 114 b may not be required to access the Internet110 via the core network 106.

The RAN 104 may be in communication with the core network 106, which maybe any type of network configured to provide voice, data, applications,and/or voice over internet protocol (VoIP) services to one or more ofthe WTRUs 102 a, 102 b, 102 c, 102 d. For example, the core network 106may provide call control, billing services, mobile location-basedservices, pre-paid calling, Internet connectivity, video distribution,etc., and/or perform high-level security functions, such as userauthentication. Although not shown in FIG. 1A, it will be appreciatedthat the RAN 104 and/or the core network 106 may be in direct orindirect communication with other RANs that employ the same RAT as theRAN 104 or a different RAT. For example, in addition to being connectedto the RAN 104, which may be utilizing an E-UTRA radio technology, thecore network 106 may also be in communication with another RAN (notshown) employing a GSM radio technology.

The core network 106 may also serve as a gateway for the WTRUs 102 a,102 b, 102 c, 102 d to access the PSTN 108, the Internet 110, and/orother networks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) andthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired or wireless communications networks ownedand/or operated by other service providers. For example, the networks112 may include another core network connected to one or more RANs,which may employ the same RAT as the RAN 104 or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, i.e., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks. For example, the WTRU 102 c shown in FIG. 1A may be configured tocommunicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram of an example WTRU 102. As shown in FIG. 1B,the WTRU 102 may include a processor 118, a transceiver 120, atransmit/receive element 122, a speaker/microphone 124, a keypad 126, adisplay/touchpad 128, non-removable memory 106, removable memory 132, apower source 134, a global positioning system (GPS) chipset 136, andother peripherals 138. It will be appreciated that the WTRU 102 mayinclude any sub-combination of the foregoing elements while remainingconsistent with an embodiment.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In another embodiment, the transmit/receiveelement 122 may be an emitter/detector configured to transmit and/orreceive IR, UV, or visible light signals, for example. In yet anotherembodiment, the transmit/receive element 122 may be configured totransmit and receive both RF and light signals. It will be appreciatedthat the transmit/receive element 122 may be configured to transmitand/or receive any combination of wireless signals.

In addition, although the transmit/receive element 122 is depicted inFIG. 1B as a single element, the WTRU 102 may include any number oftransmit/receive elements 122. More specifically, the WTRU 102 mayemploy MIMO technology. Thus, in one embodiment, the WTRU 102 mayinclude two or more transmit/receive elements 122 (e.g., multipleantennas) for transmitting and receiving wireless signals over the airinterface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as UTRA and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 106 and/or the removable memory 132.The non-removable memory 106 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. It will be appreciated that the WTRU 102 mayacquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, and the like.

FIG. 1C is a system diagram of the RAN 104 and the core network 106according to an embodiment. As noted above, the RAN 104 may employ aUTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102 cover the air interface 116. The RAN 104 may also be in communicationwith the core network 106. As shown in FIG. 1C, the RAN 104 may includeNode-Bs 140 a, 140 b, 140 c, which may each include one or moretransceivers for communicating with the WTRUs 102 a, 102 b, 102 c overthe air interface 116. The Node-Bs 140 a, 140 b, 140 c may each beassociated with a particular cell (not shown) within the RAN 104. TheRAN 104 may also include RNCs 142 a, 142 b. It will be appreciated thatthe RAN 104 may include any number of Node-Bs and RNCs while remainingconsistent with an embodiment.

As shown in FIG. 1C, the Node-Bs 140 a, 140 b may be in communicationwith the RNC 142 a. Additionally, the Node-B 140 c may be incommunication with the RNC 142 b. The Node-Bs 140 a, 140 b, 140 c maycommunicate with the respective RNCs 142 a, 142 b via an Iub interface.The RNCs 142 a, 142 b may be in communication with one another via anIur interface. Each of the RNCs 142 a, 142 b may be configured tocontrol the respective Node-Bs 140 a, 140 b, 140 c to which it isconnected. In addition, each of the RNCs 142 a, 142 b may be configuredto carry out or support other functionality, such as outer loop powercontrol, load control, admission control, packet scheduling, handovercontrol, macrodiversity, security functions, data encryption, and thelike.

The core network 106 shown in FIG. 1C may include a media gateway (MGW)144, a mobile switching center (MSC) 146, a serving GPRS support node(SGSN) 148, and/or a gateway GPRS support node (GGSN) 150. While each ofthe foregoing elements are depicted as part of the core network 106, itwill be appreciated that any one of these elements may be owned and/oroperated by an entity other than the core network operator.

The RNC 142 a in the RAN 104 may be connected to the MSC 146 in the corenetwork 106 via an IuCS interface. The MSC 146 may be connected to theMGW 144. The MSC 146 and the MGW 144 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices.

The RNC 142 a in the RAN 104 may also be connected to the SGSN 148 inthe core network 106 via an IuPS interface. The SGSN 148 may beconnected to the GGSN 150. The SGSN 148 and the GGSN 150 may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between and the WTRUs102 a, 102 b, 102 c and IP-enabled devices.

As noted above, the core network 106 may also be connected to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

A two-stage reordering procedure may be used to allow a WTRU to processand reconstruct packets transmitted from two or more Node-Bs. Thetwo-stage reordering procedure ensures in-order delivery packets tohigher layers by creating multiple MAC-ehs entities in the WTRU, one perNode-B. The two-stage reordering procedure performs reordering of thepackets in a new MAC entity only. The two-stage reordering procedurealso creates multiple MAC-ehs entities in the WTRU and performsreordering of the packets in the MAC and RLC. A single stage reorderingof packets may also be used to ensure in-order delivery of packets tohigher layers by distributing logical channels between Node-Bs to allowa WTRU to process and reconstruct packets transmitted from two or moreNode-Bs.

The term MAC-ehs may be used to represent the functionality performed ina Release 7 MAC-ehs sub-layer operating on an HS-DSCH transport channel,including, but not limited to: Hybrid Automatic Repeat Request (HARQ),disassembly, reordering queue distribution, reordering, reassembly, andLogical Channel ID Demultiplexing (LCH-ID Demux).

For inter-site operation, a new MAC architecture may be established. Inone alternative, there may be a plurality of MAC-ehs entities. Forexample, there may be a MAC-ehs entity for each site configured toperform HSDPA operation in the WTRU. For example, there may be a MAC-ehsentity for each Node B performing multipoint operation. The data istherefore split at the MAC level and one RLC entity exists per WTRU.

For intra-site operations, for example, cells belonging to the sameNode-B, there may be only one MAC-ehs entity in the WTRU. For aninter-site scenario, for example, cells belonging to different Node-Bs,there may be one MAC-ehs entity per Node-B in the WTRU. If the WTRU isconfigured for multiple cell reception, there may be an indicatortransmitted by the network telling the WTRU whether the configuration isintra-site, inter-site, or a combination of both, so that the WTRU maydetermine how many MAC-ehs entities are required. This indicator may bea simple Boolean, (for example, intra-site or inter-site indication),may be the explicit number and parameters of MAC-ehs entities that theWTRU is configured with, or may be a mapping between cells and Node-Bs(for example, cells 1 and 2 may belong to NodeB1, cell 3 may belong toNodeB2, etc.).

Other signaling mechanisms, such as the transmit power control (TPC)combination index or the relative grant (RG) combination index, may beused by the WTRU to determine whether a separate MAC-ehs entity isavailable. The WTRU's functionality may also be established for aparticular Node B. More specifically, if the WTRU is receiving HS-DSCHfrom cells that have equal indexes, then the WTRU may determine that thecells belong to the same Node B and therefore may only have one MAC-ehsentity or one set of priority queues for those cells. Otherwise, if theindexes are different, the WTRU may assume that for each HS-DSCH cellconfigured with a different index, there should be a MAC-ehs entity.Some Node B implementations may not allow sharing of resources betweenthe sectors, in which case it may be assumed that for each cell withinthis type of Node B, a MAC-ehs entity per WTRU may be configured.

On the network side, each Node B may maintain one MAC-ehs entity foreach WTRU and packets may be assigned transmit sequence numbers (TSN)independently at each Node-B. Each Node B may also maintain one MAC-ehsentity per cell for each WTRU or alternatively each Node B may maintainone MAC-ehs entity for all configured cells for the WTRU within thatsite.

FIG. 2 shows an example of a MAC architecture for a WTRU havingduplicate MAC-ehs entities. As shown in FIG. 2, the MAC architecturecontains duplicate MAC-ehs entities where complete MAC-ehsfunctionalities may be replicated. This may lead to having differentHARQ entities for each MAC-ehs entity and it may be assumed that theWTRU is configured to receive data from two different cells. Thearchitecture shown in FIG. 2 may be expanded for the cases where theWTRU may receive an HS-DSCH channel from more than two Node Bs. In FIG.2, MAC-ehs-1 201 may be established for reception of HS-DSCH-1 209 fromNode B1 and MAC-ehs-2 202 may be established for reception of HS-DSCH-2210 from Node B2. The MAC-ehs-1 201 and MAC-ehs-2 202 may furtherinclude a LCH-ID Demux entity 203, a reassembly entity 204, a reorderingentity 205, a re-ordering queue distribution 206, a disassembly entity207, and a HARQ entity 208.

The LCH-ID Demux entity 203 may be used to route the MAC-ehs ServiceData Units (SDUs) to a correct logical channel based on the receivedlogical channel identifier. The reassembly entity 204 may be used toreassemble segmented MAC-ehs SDUs and forward the MAC Protocol DataUnits (PDUs) to the LCH-ID Demux entity 203. The reordering entity 205may organize received reordering PDUs according to a received sequencenumber. The re-ordering queue distribution 206 may route the receivedreordering PDUs to a correct reordering queue based on the receivedlogical channel identifier. The disassembly entity 207 may disassembleMAC-ehs PDUs by removing the MAC-ehs header. The HARQ entity 208 handlesHARQ protocol.

In another example of a MAC architecture for WTRU, only one MAC-ehsentity may be configured with a set of re-ordering queues per cell orper Node-B. The reordering queue distribution may determine which queuethe data is transmitted to using one or a combination of the followingways.

A first way to determine which queue the data may be transmitted to isthat each HARQ ID process may be mapped to a particular MAC-ehs entity.This may be achieved by having different MAC-ehs entities use differentHARQ process IDs ranges. Optionally, a new field (e.g., a MAC-ehs ID)may be configured and used to identify a particular MAC-ehs entity inaddition to the HARQ process IDs. The different MAC-ehs entities maycontinue to use the same HARQ process ID range.

A second way to determine which queue the data may be transmitted to isthat each cell or Node-B may have a predefined range of queuedistribution IDs that enables the WTRU to discriminate between both.Optionally, a queue ID may be kept per Node B or cell.

A third way to determine which queue the data may be transmitted to isthat a mapping between the queue IDs and the MAC-ehs entity may besignaled by the network For example, the network may signal MAC-ehs IDfor each queue ID.

A fourth way to determine which queue the data may be transmitted to isthat a new identifier in the MAC-ehs Protocol Data Unit (PDU) header maybe used to indicate to the WTRU which MAC-ehs entity the MAC-ehs PDUshould be delivered.

A fifth way to determine which queue the data may be transmitted to isthat the WTRU may use a physical layer identification (for example, thescrambling code of the cell) to determine which MAC-ehs entity theMAC-ehs PDU should be delivered.

A sixth way to determine which queue the data may be transmitted to maybe based on the received HS-DSCH channel. A re-ordering queue may bemapped to a HS-DSCH transport channel or HS-DPSCH channel.

A seventh way to determine which queue the data may be transmitted to isthat a new Node-B ID indicator may be defined so that the network isable to indicate a mapping between queue ID and Node-B ID to the WTRU.Specifically the new Node-B ID indicator mapping may include whichNode-B ID each queue ID is mapped to.

FIG. 3 shows an example MAC-ehs entity and two sets of reordering queueson the WTRU side where each set of reordering queues includes twoqueues. Each MAC-ehs entity or set of reordering entities in the WTRU300 may be configured to reorder the packets for reordering queuesbelonging to a particular Node-B. The MAC-ehs entity 301 may include aLCH-ID Demux entity 303, a reassembly entity 304, a reordering-1 entity305, a reordering-2 entity 306, a re-ordering queue distribution 307, adisassembly entity 308, and a HARQ entity 309.

The LCH-ID Demux entity 303 may be used to route the MAC-ehs SDUs to acorrect logical channel based on the received logical channelidentifier. The reassembly entity 304 may be used to reassemblesegmented MAC-ehs SDUs and forward the MAC PDUs to the LCH-ID Demuxentity 303. The reordering-1 entity 305 and reordering-2 entity 306 mayorganize received reordering PDUs according to a received sequencenumber. The re-ordering queue distribution 307 may route the receivedreordering PDUs to a correct reordering queue based on the receivedlogical channel identifier. The disassembly entity 308 may disassembleMAC-ehs PDUs by removing the MAC-ehs header. The HARQ entity 309 handlesHARQ protocol. MAC-ehs 301 may be established for reception of HS-DSCH310 from the Node B.

The reordering of packets received from different Node-Bs, oralternatively cells, may be achieved, for example, in one of thefollowing ways: (1) second-stage reordering performed in the MAC bycreating a new MAC entity; or (2) second-stage reordering performed inthe RLC.

For second-stage reordering in the MAC layer, the packets delivered bythe two MAC-ehs entities or the common MAC-ehs entity may not be inorder because the packets from different Node Bs may not necessarily bereceived at the same time. Because RLC functionality may rely on theMAC-ehs entity to deliver RLC PDUs in order, existing procedures, suchas RLC status reporting, may be affected. With a MAC architecture havingduplicate MAC-ehs entities, the RLC entity may receive packets out oforder, which may trigger premature RLC status reporting from the WTRUside and therefore unnecessary retransmission of data that may not belost but rather delayed. In order to avoid or to minimize the impact tothe RLC entity, the MAC architecture may ensure that packets coming fromtwo Node Bs are properly reordered prior to being transmitted to RLC orhigher layer entities in the WTRU. This new MAC functionality may befound in a MAC-sf entity.

FIG. 4 shows an example of a MAC architecture for a WTRU havingduplicate MAC-ehs entities and a MAC-sf entity. Each WTRU may beconfigured with one MAC-sf entity. The new MAC-sf entity may be foundabove the one or more MAC-ehs entities or above a common MAC-ehs entity.In the Universal Terrestrial Radio Access Network (UTRAN) there is oneMAC-sf entity for each WTRU.

As shown in FIG. 4 a MAC-sf 403 may communicate with MAC-ehs entities401 or a common MAC-ehs entity 402 and with a MAC-d 404 as shown in FIG.4.

A MAC-c/sh/m 407 may control access to all common transport channels,except the HS-DSCH transport channel and the E-DCH transport channel.The MAC-d 404 may control access to all dedicated transport channels, tothe MAC-c/sh/m 407 and MAC-hs/ehs 401 and 402. The MAC-c/sh/m 407 mayalso control access to a MAC-is/i 405. MAC-hs/ehs 401 and 402 may alsohandle HSDPA specific functions and control assess to the HS-DSCHtransport channel. The MAC-es/e or MAC-is/i 405 may control access tothe E-DCH transport channel.

FIG. 5 shows an example of a global MAC-ehs entity in a WTRU having twoglobal reordering sub-entities. All of the MAC-sf functionalities may bemerged in a global MAC-ehs entity or a new MAC entity with the MAC-ehsfunctionalities on the WTRU side. The MAC-sf functionalities may residein a new sub-entity, which may be called a global reordering entity 502.There may be one global reordering entity 502 per logical channelidentity 503. A MAC-ehs entity 501 may include a LCH-ID Demux entity503, a reassembly entity 504, a reordering-1 entity 505, a reordering-2entity 506, a re-ordering queue distribution 507, a disassembly entity508, and a HARQ entity 509. As shown in FIG. 5, there may be tworeordering queues per Node-B and each Node-B may use the same twological channels. The MAC-sf functionalities may also be included in theMAC-d sublayer.

The LCH-ID Demux entity 503 may be used to route the MAC-ehs SDUs to acorrect logical channel based on the received logical channelidentifier. The reassembly entity 504 may be used to reassemblesegmented MAC-ehs SDUs and forward the MAC PDUs to LCH-ID Demux entity303. The reordering-1 entity 505 and reordering-2 entity 506 mayorganize received reordering PDUs according to a received sequencenumber. The re-ordering queue distribution 507 may route the receivedreordering PDUs to a correct reordering queue based on the receivedlogical channel identifier. The disassembly entity 508 may disassembleMAC-ehs PDUs by removing the MAC-ehs header. The HARQ entity 509 handlesHARQ protocol. MAC-ehs 501 may be established for reception of HS-DSCH510 from the Node B.

FIG. 6 shows an example of a MAC-sf entity on the UTRAN side. On theUTRAN side, a new MAC-sf entity 602 may be located in the RNC and maycommunicate with both MAC-ehs entities 601 in the Node-Bs and with aMAC-d 603 in the RNC. FIG. 6 shows that the new MAC-sf entity 602 may belocated in the RNC and may communicate with both MAC-ehs entities 601 inthe Node-Bs and with the MAC-d 603 in the RNC.

A MAC-c/sh/m 606 may be located in a controlling RNC while the MAC-d 603may be located in a serving RNC. MAC-hs/ehs 601 may be located in a NodeB. The MAC-d PDUs to be transmitted may be transferred from theMAC-c/h/m 606 to MAC-hs/ehs 601 via Iub interface or from the MAC-d 603via Iur/Iub.

In the WTRU, each MAC-ehs entity may be configured to deliver thereordered packets per Node-B, or alternatively per cell, to the MAC-sfentity which may reorder them by using the new sequence number SN_(sf)before delivering them to the RLC.

FIG. 7 shows an example of a MAC-sf entity on the WTRU side. The MAC-sfentity may include a disassembly entity and a reordering entity perlogical channel identity. In FIG. 7, for example, there are a total offour logical channels that may be assumed. FIG. 7 shows a MAC-sf entity701 including reordering entities 702 and disassembly entities 703. Thereordering entities 702 may organize received reordering PDUs accordingto a received sequence number. The disassembly entities 703 maydisassemble MAC-ehs PDUs by removing the MAC-ehs header.

FIG. 8 shows an example of a MAC-sf entity and duplicated MAC-ehsentities on the WTRU side. As shown in FIG. 8, a MAC-sf entity 801 maybe represented with one of the MAC-ehs entities described above, whereintwo separate MAC-ehs entities may coexist. The MAC-sf entity 801 may belocated on top of the two MAC-ehs entities 804 and 805 and may receivepackets that have been demultiplexed according to the logical channelidentity they may be mapped to. The MAC-sf entity 801 may includereordering entities 802 and disassembly entities 803. Each MAC-ehsentity 804 and 805 may include a LCH-ID Demux entity 806, a reassemblyentity 807, a reordering 8 entity 08, a re-ordering queue distribution809, a disassembly entity 810, and a HARQ entity 811.

The reordering entities 802 may organize received reordering PDUsaccording to a received sequence number. The disassembly 803 maydisassemble MAC-ehs PDUs by removing the MAC-ehs header.

The LCH-ID Demux entity 806 may be used to route the MAC-ehs SDUs to acorrect logical channel based on the received logical channelidentifier. The reassembly entity 807 may be used to reassemblesegmented MAC-ehs SDUs and forward the MAC PDUs to the LCH-ID Demuxentity 303. The reordering entity 808 may organize received reorderingPDUs according to a received sequence number. The re-ordering queuedistribution 809 may route the received reordering PDUs to a correctreordering queue based on the received logical channel identifier. Thedisassembly entity 810 may disassemble MAC-ehs PDUs by removing theMAC-ehs header. The HARQ entity 811 handles HARQ protocol. MAC-ehs 804and 805 may be established for reception of HS-DSCH 812 from the Node B.

FIG. 9 shows an example MAC-sf PDU. In FIG. 9, it may be assumed thatonly two logical channels have been configured and that data for bothlogical channels may have been transmitted by each Node-B. The packetsbelonging to the same logical channel may be transmitted to the samedisassembly and reordering entity. FIG. 9 serves only as an example andthe MAC-sf entity may similarly co-exist with all the otherarchitectures described above.

In the MAC-ehs entity, the existing functionality of the “LCH-IDdemultiplexing” may be updated such that the MAC-ehs demultiplexingentity routes the MAC-sf PDUs (for example, the MAC-ehs SDUs) to thecorrect disassembly and reordering entity of the MAC-sf entity based onthe received logical channel identifier. In other words, the MAC-ehsdemultiplexing entity may be configured to transmit the MAC-ehs SDUsbelonging to the same logical channel to the same disassembly andreordering entity.

In the RNC, a new MAC sequence number SN_(sf) may be added as a headerto each MAC-sf PDU to help the MAC-sf entity in the WTRU reorder thepackets. The MAC-sf entity in the RNC may be responsible for managingand setting a sequence number per MAC-d flow or per logical channel.Each MAC-d PDU may be given a sequence number. The data may then betransmitted to the MAC-ehs entity of one or more of the configuredHS-DSCH Node Bs.

A MAC-sf PDU may be defined with a payload 905 and a header 903. TheMAC-sf payload 905 may correspond to one MAC-sf Service Data Unit (SDU)904 while the header 903 may include the new SF Sequence Number, forexample SNsf 902 as shown in FIG. 9. FIG. 9 also shows that on thetransmitter side, for example, UTRAN, the MAC-d may transmit a MAC-d PDU901 to the MAC-sf entity, the MAC-sf entity may receive it as a MAC-sfSDU, and the MAC-sf entity may transmit it to the MAC-ehs entity whichmay receive it as a MAC-ehs SDU 907.

On the WTRU side, the MAC-sf disassembly entity may receive the MAC-sfPDUs out of order from the two MAC-ehs entities or from the commonMAC-ehs entity. The MAC-sf disassembly entity may remove the MAC-sfheader and may deliver the MAC-sf reordering PDU to the MAC-sfreordering entity. There may be one reordering entity per logicalchannel or per MAC-d flow. Optionally, there may also be one disassemblyentity per logical channel. The MAC-sf reordering entity may reorder thepackets according to the SN_(sf) included in the header beforedelivering the packets (for example, the MAC-sf SDUs equivalent to theMAC-d PDUs) to the MAC-d to the correct logical channel.

Additional functionality may be defined for the MAC-sf entity toproperly reorder the MAC-sf PDUs. Moreover, the reordering entity maynot wait for a missing MAC-sf PDU for an undetermined period of time,because this PDU may be lost or the Node-Bs may be so desynchronizedthat the delay between packets from one Node-B compared to the packetsfrom the other Node-B may become unacceptable.

FIGS. 10A and 10B are a flow diagram that shows an alternativeembodiment where only one Tsf timer is used at a given time. Thefollowing terms are used herein. “Next_expected SNsf” may be the SF-DCsequence number (SNsf) following the SNsf of the last in-sequence MAC-sfPDU received. The initial value of Next_expected_SNsf may be zero. “Tsf”may be the SF-DC missing PDU timer. There may be one timer Tsf runningat a given time.

The following describes how the SF-DC reordering entity may use Tsf,Next_expected SNsf and the reordering buffer to reorder the packets thatit receives as illustrated in FIGS. 10A and 10B. A determination is madeas to whether the Tsf has expired or a PDU is received 1000. If a PDU isreceived, determine whether the received PDU is within range 1001. Ifthe received PDU is within range, i.e. SNsf≧Next_expected_SNsf,determine if Tsf is running 1002, If Tsf is not running and a MAC-sf PDUis received in order 1003 (SNsf=Next_expected_SNsf), the SF-DCreordering entity may deliver 1004 this PDU to the MAC-d and increment1005 the value of Next_expected_SNsf by one. If a missing PDU isdetected 1003 by the WTRU (a MAC-sf PDU with SNsf>Next_expected SNsf isreceived) and no timer Tsf is already running Tsf may be started 1006and the received PDU may be stored 1007 in the reordering buffer at theplace indicated by its SNsf.

While Tsf is running 1002, the reordering entity may store the receivedPDU in their SNsf order in the reordering buffer 1018. If the detectedmissing PDU is received 1009 in time (the MAC-sf PDU withSNsf=Next_expected SNsf is received before Tsf expires) the timer Tsfmay be stopped 1010. The received PDU may be stored 1011 on thereordering buffer at the place indicated by its SNsf. If one or morePDUs are still missing 1012 in the reordering buffer, Tsf may berestarted 1013, Next_expected_SNsf may be set 1014 to the smallest SNsfamong all the missing PDUs, and PDUs with SNsf<Next_expected SNsf may bedelivered 1015 to the MAC-d. If no PDUs are missing 1012 in thereordering buffer, Next_expected_SNsf may be set 1016 to the SNsf of thePDU having the highest SNsf in the reordering buffer plus one(Next_expected_SNsf=highest SNsf+1) and all of the PDUs stored in thebuffer may be delivered 1017 to the MAC-d.

If Tsf expires 1000 if there is at least another missing 1020 PDU in thereordering buffer, Tsf may be restarted and Next_expected SNsf may beset 1021 to the SNsf of the missing PDU having the smallest SNsf. Ifthere is no other missing 1020 PDU in the reordering buffer,Next_expected_SNsf may be set 1022 to the SNsf of the PDU having thehighest SNsf in the reordering buffer plus one(Next_expected_SNsf=highest SNsf+1). The MAC-sf PDU which have beenstored in the reordering buffer and which have a SNsf<Next_expected SNsfmay be delivered 1019 to the MAC-d. If the SF-DC reordering entityreceives a PDU 1000 with SNsf<Next_expected_SNsf 1001, it may discard it1008.

FIGS. 11A and 11B are a flow diagram that shows an alternativeembodiment where one timer Tsf is used per missing PDU. The followingvariables may be defined as follows. “Next_SNsf” may be the SF-DCsequence number (SNsf) following the SNsf of the last MAC-sf PDUreceived or missing. The initial value of Next_SNsf may be zero.“Tsf(SNsf)” may be the SF-DC missing PDU timer. There may be one timerper missing PDU. “Missing_Pdu(SN)” may be the SN of a missing PDU havingsequence number SN. There may be one variable per missing PDU.

The following describes how the SF-DC reordering entity may use theTsf(SNsf) timers, the different variables, and the reordering buffer toreorder the packets it receives as illustrated in FIGS. 11A and 11B. Adetermination is made as to whether the Tsf(SNsf) has expired or a PDUis received 1100. If a PDU is received, determine whether the receivedPDU is within range 11101. If the received PDU is within range, i.e.SNsf≧smallest Missing_Pdu(SN), determine if Tsf(SNsf) is running 1102.If no timer Tsf(SNsf) is running and a MAC-sf PDU is received in order1103 (SNsf=Next_SNsf) the SF-DC reordering entity may deliver 1104 thisPDU to the MAC-d and may increment 1105 the value of Next_SNsf by one.If a missing PDU is detected by the WTRU 1103 (a MAC-sf PDU withSNsf>Next_SNsf is received) a new variable “Missing_Pdu(SNsf)” may beset 1106 to the value of Next_SNsf. An instance of Tsf(SNsf) may bestarted 1107 for this missing PDU. The received PDU may be stored 1108in the reordering buffer at the place indicated by its SNsf. The valueof Next_SNsf may be incremented 1109 by one until its value is differentfrom the SNsf of the recently received PDU. The preceding may beaccomplished in any combination and in any order. If one or moreinstances of Tsf(SNsf) are running 1102, the reordering entity may storethe PDU received in the SNsf order in the reordering buffer 1117. If adetected missing PDU is received 1111 in time (if a MAC-sf PDU with SNsfequal to one of the Missing_Pdu(SNsf) variables is received before thecorresponding Tsf(SNsf) expires) the corresponding timer Tsf(SNsf) maybe stopped 1112. The received PDU may be stored 1113 in the reorderingbuffer at the place indicated by its SNsf. If Missing_Pdu(SNsf) is theonly missing PDU 1114 (if no timers Tsf are running anymore), all of thestored PDUs may be delivered 1116 to the MAC-d. In the case of multiplemissing PDUs 1114 (if at least one timer Tsf(SNsf) is still running) andif Missing_Pdu(SNsf) is the smallest among all the Missing_Pdu(SNsf),the stored PDUs having an SNsf<next Missing_Pdu(SNsf) may be delivered1115 to the MAC-d. The preceding may be accomplished in any combinationand in any order.

If an instance Tsf(SNsf) expires 1100 if there is no other Tsf timerrunning 1114, all of the stored PDUs may be delivered 1119 to the MAC-d.If this Tsf(SNsf) corresponds 1116 to the smallest Missing_Pdu(SNsf),the stored PDUs having SNsf<next Missing_Pdu(SNsf)−1 may be delivered1120 to the MAC-d. If Next_SNsf is equal to this Missing_Pdu(SNsf)+1,Next_SNsf may be incremented 1118 by one. The preceding may beaccomplished in any combination and in any order. If the SF-DCreordering entity receives a PDU 1100 with SNsf<smallest Missing_Pdu(SN)1101, it may discard it 1110.

The value of Tsf may be fixed, may be determined by the WTRU, or may beconfigured by the network. The network may signal a minimum and amaximum value for Tsf. If the value of Tsf is configured by the network,it may be based on the network knowledge about the level ofsynchronization between the two NodeBs. For instance if the network isaware that the Node-Bs are transmitting at approximately the same time,it may configure the WTRU with a low value of Tsf. If the network knowsthat one Node-B transmits data a long period of time after the otherNode-B, it may configure the WTRU with a long value of Tsf. In case ofdeactivation of the secondary single frequency HS-DSCH serving cell, theMAC-sf entity may be removed. The value of the timer Tsf may be set tozero.

The MAC layer second stage reordering may be based on the MAC-ehsTransmission Sequence Number (TSN) by splitting the range of allowed TSNvalued per Node B (or alternative transmitting cell). The RNC mayforward sequential blocks of MAC-d PDUs to each Node B and may assignnon-overlapping ranges of TSN values, where the range of TSN values mayindicate the sequence of blocks between the multiple Node Bs.

In one example realization, the RNC may transmit the first sequence often consecutive MAC-d PDUs to Node B2 with allowed TSN ranges 101-200.Upon reordering at the WTRU, the WTRU may first reorder PDUs within eachTSN range (first stage reordering) and then may reorder based on TSNrange (second stage reordering). In this example, the WTRU may deliverall data blocks received using TSN ranges 1-100 to the RLC first, andthen may deliver all data blocks received using TSN ranges 101-200 tothe RLC.

Alternatively or additionally, reordering may be performed in the RLC.The RLC may receive the packets from the MAC reordered per Node-B, oralternatively per cell, only and may perform the global reordering ofpackets from different MAC instances. If the WTRU has been configuredwith multiple MAC-ehs entities, the RLC may be configured with a newoption indicating that the WTRU has to do reordering in RLCAcknowledgement Mode (AM). For example, the MAC may no longer berequired to ensure in-order delivery of RLC PDUs from different sites.The RLC itself, if it detects a missing Sequence number, may optionallywait for a given period of time to ensure that the missing PDU or PDUsare not being transmitted by the other Node B, prior to triggering a RLCstatus report. The RLC reordering procedure may be applied for deliverof RLC SDUs to higher layers and/or status reporting to the transmitterside for the RLC AM

The procedures in the RLC may be performed for acknowledgement mode (AM)logical channels and optionally unacknowledged mode RLC. FIGS. 12A and12B are a flow diagram that shows an alternative embodiment where onetimer is used per missing sequence number. A new timer called, forexample, Timer_Am_Reordering may be defined and used to postpone thetransmission of a STATUS PDU in case an AM Data (AMD) PDU is missing.The following definitions may be used. “Timer_Am_Reordering” may be amissing PDU timer. There may be one timer running at a given time.“VR(AM_NEXT)” may be a Sequence Number of the next expected PDU, forexample, the SN following the SN of the last PDU received in-sequence.This variable may be initialized to zero. “Reordering_Window_Size” maybe the size of the reception window where the WTRU RLC may receive aPDU. If a PDU is received with an SN before the window starts, the RLCshould discard it. “VR(BW)” may be beginning of the window. Thisvariable may be initialized to zero. “VR(EW)” may be the end of thewindow. This variable may be initialized to Reordering_Window_Sizeminus 1. All operations may calculate modulo the maximum SN.

The following may describe the RLC behavior for this first solution asshown in FIGS. 12A and 12B. A determination is made as to whetherTimer_AM_Reordering has expired or a PDU is received 1200. If a PDU isreceived, determine whether the received PDU is within range 1201. Ifthe received PDU is within rang, i.e. SN≧VR(BW), determine ifTimer_AM_Reordering is running 1202. If Timer_Am_Reordering is notrunning and if the RLC receives a PDU in sequence order 1203 (the SN ofthe received PDU is equal to VR(AM_NEXT)), it stores 1204 it in thereordering buffer at the place indicated by its SN and increment 1205VR(AM_NEXT) by one. If the RLC may reassemble a RLC SDU by using theordered PDUs from the reordering buffer, it may deliver 1204 the SDU tothe upper entity. If the RLC detects a gap 1203 in the reception (thereceived PDU has an SN>VR(AM_NEXT)) if Timer_Am_Reordering is notrunning, it may start 1206 Timer_Am_Reordering. The received PDU may bestored 1207 in the reordering buffer at the place indicated by SN. WhileTimer_Am_Reordering is running 1202, the RLC may store the received PDUsin their SN order in the reordering buffer, leaving gaps 1217 if PDUsare missing.

If the detected missing PDU is received in time 1209 (if a PDU with anSN equal to VR(AM_NEXT) is received before Timer_Am_Reordering expires)Timer_Am_Reordering may be stopped 1210. The received PDU may be stored1211 in the reordering buffer at the place indicated by its SN. Anacknowledgement (ACK) may be transmitted 1212 to the network for thisPDU. If in the reordering buffer, one or more PDUs are still missing1213 (gaps exist in the SN), Timer_Am_Reordering may be restarted 1214or VR(AM_NEXT) may be set 1215 to the smallest SN among all of themissing PDUs of the reordering buffer. If no PDUs are missing 1213 inthe reordering buffer (no gap exists in the SN): VR(AM_NEXT) may be set1216 to the SN of the PDU having the highest SN in the reordering bufferplus one (VR (AM_NEXT)=highest SN+1). If the RLC may reassemble an RLCSDU from the stored PDU, the SDU may be delivered to the upper layer(e.g. all the RLC PDUs for a given RLC SDU are received). The precedingmay be accomplished in any combination and in any order.

If Timer_Am_Reordering expires 1200 STATUS PDU may be transmitted 1218to the network indicating a negative acknowledgement (NACK) for the SNequal to VR(AM_NEXT) and if other PDUs are missing 1219 in thereordering buffer with an SN smaller than VR(AM_NEXT), a NACK may beindicated for the missing SN in the STATUS PDU as well and optionally anACK for all received PDUs may also be reported. If there is at leastanother missing 1220 PDU in the reordering buffer which is in thereception window, Timer_Am_Reordering may be restarted 1221 orVR(AM_NEXT) may be set 1222 to the SN of the missing PDU. If there areno more PDUs missing 1220 in the reordering buffer, VR(AM_NEXT) may beset 1223 to the SN of the PDU with the highest SN plus one(VR(AM_NEXT)=highest SN+1). The preceding may be accomplished in anycombination and in any order.

If the RLC receives a PDU 1200 with an SN that is before the beginningof the reception window (SN<VR(BW)) 1201, it may discard the PDU 1208.If the WTRU receives a PDU 1200 with a higher SN than VR(EW) 1201, theWTRU may move the reception window up to this SN 1224, i.e.VR(BW)=VR(BW)+(SN−VR(EW)) and VR(EW)=SN. The WTRU may reassemble the RLDSDU with the PDUs stored in the reordering buffer, if possible, andtransmit the SDU to the upper entity 1225. The WTRU may remove the PDUsfor which SN is below the reception window from the reordering buffer1226. The preceding may be accomplished in any combination and in anyorder.

Alternatively or additionally, one timer may be used per missing PDU. Anew instance of the reordering timer may be started per missing PDU. Thefollowing definitions may be used herein. “Timer_SR(SNm)” may be amissing PDU timer. There may be one instance of Timer_SR per missingPDU. “Missing_Var(SNm)” may be the missing PDU Sequence Number. Theremay be one instance of Missing_Var(SNm) per missing PDU. “VR(NEXT)” maybe the Sequence Number of the PDU with highest SN plus one. Thisvariable may be initialized to zero. “Reordering_Window_Size” may be thesize of the reception window in which the WTRU RLC may receive a PDU. Ifa PDU is received with an SN before the window starts, the RLC maydiscard it. “VR(BW)” may be the beginning of the window. This variablemay be initialized to zero. “VR(EW)” may be the end of the window. Thisvariable may be initialized to Reordering_Window_Size minus 1.

FIGS. 13A and 13B are a flow diagram that shows the RLC behavior. Adetermination is made as to whether Timer_SR(SNm) has expired or a PDUis received 1300. If a PDU is received, determine whether the receivedPDU is within range 1301. If the received PDU is within range, i.e.SN≧VR(BW), determine if Timer_SR(SNm) is running 1302. If no instance ofTime_SR is running 1302 and if the RLC receives a PDU in sequence order1303 (the SN of the received PDU is equal to VR(NEXT)), it may stores1304 the PDU in the reordering buffer at the place indicated by its SNand increment 1305 VR(NEXT) by one. Each time the RLC may reassemble aRLC SDU by using the ordered PDUs from the reordering buffer, it maydeliver the SDU to the upper entity. If the RLC detects a gap 1303 inthe reception (the received PDU has an SN>VR(NEXT)) an instance ofTimer_SR(SNm) may be started 1306 for the missing PDU. The SNm of thismissing PDU may be saved 1307 in an instance of the variableMissing_Var(SNm). The received PDU may be stored 1308 in the reorderingbuffer at the place indicated by SN. VR(NEXT) may be set 1309 equal tothe missing PDU SNm plus one (VR(NEXT)=Missing_Var(SNm)+1). Thepreceding may be accomplished in any combination and in any order.

If one or more instances of Timer_SR are running 1302, the RLC may storethe PDUs received in-sequence (without gaps) in their SN order in thereordering buffer and may increment VR(NEXT) by one 1316. If thedetected missing PDU is received in time 1311, (if a PDU with an SNequal to one of the instances of Missing_Var(SNm) is received before thecorresponding Timer_SR(SNm) expires) the corresponding timerTimer_SR(SNm) may be stopped 1312. The received PDU may be stored 1313in the reordering buffer at the place indicated by its SN. An ACK may betransmitted 1314 to the network for the PDU. If the RLC may reassemblean RLC SDU from the stored PDU, the SDU may be delivered 1315 to theupper layer. The preceding may be accomplished in any combination and inany order.

If one of the instances of Timer_SR(SNm) expires 1300 a STATUS PDU maybe transmitted 1317 to the network indicating a NACK for the SN equal toMissing_Var(SNm) of this missing PDU. The RLC may restart 1318Timer_SR(SNm). If the RLC receives a PDU 1300 with an SN that is beforethe beginning of the reception window (SN<VR(BW)) 1301, it may discardthe PDU 1310. If the WTRU receives a PDU 1300 with a higher SN thanVR(EW) 1301 the reception window may be moved up 1319 to this SN(VR(BW)=VR(BW)+(SN−VR(EW)) and VR(EW)=SN). The instances of Timer_SR forwhich corresponding Missing_Var values are below the new window may bestopped and the instances of the corresponding Missing_Var variables maybe deleted 1320. The RLC SDU with the PDUs stored in the reorderingbuffer may be reassembled, if possible, and the SDU may be transmittedto the upper entity 1321. The PDUs for which SN is below the receptionwindow may be removed from the reordering buffer 1322. The preceding maybe accomplished in any combination and in any order. Timer_SR may have afixed value, may be determined by the WTRU, or may be configured by thenetwork in a Radio Resource Control (RRC) message.

There may be limitations on the waiting duration and limitations on thenumber of requests for a missing packet. After a maximum number ofretransmissions for a particular PDU, the RLC on the network side may beto reset. However, some controls may be implemented on the WTRU side aswell as follows. The WTRU RLC may limit the number of times it mayrequest a retransmission for the same missing PDU according to thefollowing.

A new variable called, for example, V_RN may be defined per missing PDUinitialized to zero and may be used to track how many times Timer_SR hasbeen started for a particular PDU identified by an SN. If the RLCtransmits the STATUS_PDU due to a missing PDU, it may start Timer_SRagain for the PDU and may increment the new variable V_RN by one forthis PDU. A maximum number of retries may be defined and may be calledMAX_RN. If V_RN becomes greater than MAX_RN for a particular missing PDUand the Timer_SR expires while this PDU has still not been received,this PDU may be considered lost, and the RLC may discard all of the PDUsbelonging to the same SDU that the missing PDU and may optionallytransmit a STATUS_PDU or another type of indicator to the networkindicating that it is not waiting for this PDU anymore including the SNof the PDU. MAX_RN may be a fixed value, determined by the WTRU orconfigured by the network. Additionally, it may depend on the value ofthe existing variable MaxDAT which represents the maximum number ofretransmissions of an AMD PDU plus one. For example, it may be equal toMaxDAT or it may be equal to MaxDAT minus a constant value. V_RN may bea static or dynamic variable. It may be reset to zero if the missing PDUis received, or if the maximum value of V_RN (MAX_RN) is reached.

Additionally, there may be a maximum number of missing PDUs the RLC maywait for simultaneously. This may translate in a maximum number ofTimer_SR that may run at the same time. For example, if the RLC detectsa missing PDU, it may only start a new Timer_SR if the maximum number ofTimer_SR has not been reached. Otherwise, it may consider this PDU aslost and discard all of the PDUs belonging to the same SDU and it mayoptionally transmit a STATUS_PDU or another indication to the peer RLCon the network side indicating that it may not wait for this PDU anymoreincluding the SN of this PDU.

Alternatively, another timer called, for example, Timer_MaxRN may bedefined. The time, Timer_MaxRN, may take a value not dependent onTimer_SR, or the value may be a multiple of Timer_SR. One of the minimumconditions on the setting of Timer_MaxRN may be that Timer_MaxRN has tobe longer that Timer_SR. The WTRU RLC may start the timer Timer_MaxRN atthe same time it starts Timer_SR for a particular missing PDU the firsttime this PDU is detected as missing. This may be accomplished insteadof when the retransmissions of the PDU are also missing. If T_RNexpires, Timer_MaxRN may still be running. If the missing PDU arrives,T_RN and T_MaxRN may be stopped. If Timer_MaxRN expires, the WTRU mayconsider the missing PDU as lost, stop Timer_SR, discard all the PDUsbelonging to the same SDU as the missing PDU, and optionally transmit aSTATUS_PDU to the network indicating that the WTRU may not wait for thismissing PDU anymore, including the SN of this PDU.

In case the WTRU transmits a STATUS PDU to indicate to the network thatit may not wait for a missing PDU with a certain SN or several missingPDUs, a new super-field (SUFI) type may be defined by using one of thereserved SUFI types bit combinations between 1001-1111. This new SUFItype may be called for example “No More Retries.” The “No More Retries”SUFI may include the SN of one missing PDU or a list of missing PDUs forwhich the WTRU RLC will not wait for a retransmission anymore. If thenetwork receives this indication from the WTRU, it may start an RLCreset procedure.

Unacknowledgement Mode (UM) may be used where the existing “out ofsequence SDU delivery” functionality of the RLC UM may be reused toreorder the PDUs received from the MAC if two MAC-ehs entities areconfigured. This may allow the RLC UM on the WTRU and on the UTRAN sideto be configured with “out of sequence SDU delivery” for DCCH and DTCHlogical channels, in addition to the MCCH logical channel.

In the case of no second stage reordering, logical channels may bedistributed between Node-Bs. Node-Bs transmitting to a same WTRU mayonly transmit over different logical channels. For example, one Node-Bmay transmit control information by using Signaling Radio Bearers(SRBs), while the other Node-B may transmit data using Radio Bearers(RBs). Another example may be that one Node-B may transmit data with RB1while the other Node-B may transmit data with RB2 (for example, VoIP andWeb browsing). Because there is one reordering queue per logicalchannel, existing MAC and RLC procedures may be used with this solution.

When dynamic switching and synchronization may be used between Node-Bs,the node-Bs may not transmit data simultaneously to the WTRU. Instead,the transmitting Node-B may be switched dynamically, meaning thatNode-Bs may transmit one after another every x number of TransmissionTime Intervals (TTIs). In this case, in order to minimize the impact onthe WTRU (to minimize the changes required in the MAC), somesynchronization regarding the TSN may be designed between the twoNode-Bs. Instead of having the transmission sequence number generatedindependently on each Node-B, the transmission sequence numbers may besynchronized between Node-Bs, so that there is one common sequencenumbering between the Node-Bs. For example, the TSN received at the WTRUin the MAC-ehs entity may be unique even if different Node-Bs aretransmitting.

In one alternative, if one Node-B is finished with its currenttransmission, it may indicate the last TSN it has used to the otherNode-B over the Iub or Iur interface, so that the other Node-B may startits new transmission with the TSN following the TSN received from theother Node-B.

If the WTRU detects an order or an indication that the Node Bs arechanging, the WTRU may signal in the uplink (UL) direction using a MACPDU (for example, a MAC-i PDU or a control MAC PDU) the last TSN numberit received for each reordering queue.

Alternatively or additionally, each Node-B may reset its TSN when itstarts a new transmission. The WTRU, if it detects a change on Node B orcell, may reset its next_expected_TSN variable, may reinitialize itsRcvWindow_UpperEdge variable, or may stop timer T1 if running every timeit detects it is receiving data from a different Node-B. The WTRU maydetect whether it is receiving from a particular Node-B as describedabove and may optionally flush its HARQ buffers.

Different HARQ architectures may be defined depending on thetransmission design chosen for SF-DC. If the two Node-Bs transmit thesame set of data, soft combining may be achieved in the WTRU. One HARQentity may be required in the MAC-ehs entity on the WTRU side. If thetwo Node-Bs transmit different set of data simultaneously, two HARQentities may be designed in the WTRU as shown in FIGS. 2-9. Two sets ofHARQ processes may also be configured (for example, 12 where there are 6HARQ processes per cell), but the HARQ processes may be shared acrossall cells.

In case of dynamic switching as described above (each Node-B transmits adifferent set of data but not simultaneously), there may be two HARQentities in the MAC or one common HARQ entity shared by both Node-Bswhich may allow packets transmitted from one Node-B to be retransmittedby the other Node-B. In case of a common HARQ entity, Node-Bs have tosynchronize their NDI.

In one example, if one Node-B is finished with its current transmission,it may indicate to the other Node-B the last value of the New DataIndicator (NDI) it has used on each HARQ process so that the otherNode-B may properly set the value of the NDI it transmits to the WTRU.

Alternatively or additionally, each Node-B may reset its NDI to zero ifit starts a new transmission and the WTRU may consider that it is afirst transmission in the HARQ process if it detects that it isreceiving from a different Node-B.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element may be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs). A processor in association withsoftware may be used to implement a radio frequency transceiver for usein a WTRU, UE, terminal, base station, RNC, or any host computer.

What is claimed:
 1. A method for use in a wireless transmit receive unit(WTRU) for two-stage reordering of received protocol data units (PDUs),the method comprising: receiving PDUs from a plurality of Node-Bs,wherein each of the received PDUs has a transmission sequence number(TSN); reordering the received PDUs from each of the plurality ofNode-Bs using the TSN in a MAC layer in different reordering queues;delivering the received PDUs from a plurality of reordering queues toone logical channel in an RLC layer; reordering the received PDUs in theRLC layer based on a sequence number (SN); starting a timer when atleast a RLC PDU is missing based on SN of the RLC PDU; and transmittinga status report indicating a missing RLC PDU based on SN of the RLC PDUon a condition that the timer expires, wherein transmission of thestatus report is delayed on a condition that a RLC PDU is missing basedon SN of the RLC PDU and the timer is running.
 2. The method of claim 1further comprising: restarting the timer; and setting a SN of a nextexpected RLC PDU to the SN of the missing RLC PDU on a condition thatthe timer expires and at least one other RLC PDU is missing.
 3. Themethod of claim 1 further comprising: setting a SN of a next expectedRLC PDU to the SN of the RLC PDU with a highest SN plus one on acondition that the timer expires and no other RLC PDU is missing.
 4. Themethod of claim 1 wherein the transmitted status report indicates anegative acknowledgement (NACK) if other RLC PDUs are missing in areordering buffer with a SN smaller than the SN of a next expected RLCPDU.
 5. A method for use in a UTRAN for two-stage reordering of receivedprotocol data units (PDUs), the method comprising: receiving PDUs from aplurality of Node-Bs, wherein each of the received PDUs has atransmission sequence number (TSN); reordering the received PDUs fromeach of the plurality of Node-Bs using the TSN in a MAC layer indifferent reordering queues; delivering the received PDUs from aplurality of reordering queues to one logical channel in an RLC layer;reordering the received PDUs in the RLC layer based on a sequence number(SN); starting a timer when at least a RLC PDU is missing based on SN ofthe RLC PDU; and transmitting a status report indicating a missing RLCPDU based on SN of the RLC PDU on a condition that the timer expires,wherein transmission of the status report is delayed on a condition thata RLC PDU is missing based on SN of the RLC PDU and the timer isrunning.
 6. The method of claim 5 further comprising: restarting thetimer; and setting a SN of a next expected RLC PDU to the SN of themissing RLC PDU on a condition that the timer expires and at least oneother RLC PDU is missing.
 7. The method of claim 6 wherein thetransmitted status report indicates a negative acknowledgement (NACK) ifother RLC PDUs are missing in a reordering buffer with a SN smaller thanthe SN of a next expected RLC PDU.
 8. The method of claim 5 furthercomprising: setting a SN of a next expected RLC PDU to the SN of the RLCPDU with a highest SN plus one on a condition that the timer expires andno other RLC PDU is missing.
 9. A wireless transmit receive unit (WTRU)for two-stage reordering of received protocol data units (PDUs), theWTRU comprising: a receiver configured to receive PDUs from a pluralityof Node-Bs, wherein each of the received PDUs has a transmissionsequence number (TSN); a first reordering entity configured to reorderthe received PDUs from each of a plurality of Node-Bs using the TSN in aMAC layer in different reordering queues; a processor configured todeliver the received PDUs from a plurality of reordering queues to onelogical channel in an RLC layer; a second reordering entity configuredto reorder the received PDUs in the RLC layer based on a sequence number(SN); a timer configured to start when at least a RLC PDU is missingbased on SN of the RLC PDU; and a transmitter configured to transmit astatus report indicating missing RLC PDU based on SN of the RLC PDU on acondition that the timer expires, wherein the transmission of the statusreport is delayed on a condition that a RLC PDU is missing based on SNof the RLC PDU and the timer is running.
 10. The WTRU of claim 9 furthercomprising: the timer further configured to restart; and the processorfurther configured to set a SN of a next expected RLC PDU to the SN ofthe missing RLC PDU on a condition that the timer expires and at leastone other RLC PDU is missing.
 11. The WTRU of claim 9 furthercomprising: the processor further configured to set a SN of a nextexpected RLC PDU to the SN of the RLC PDU with a highest SN plus one ona condition that the timer expires and no other RLC PDU is missing. 12.The WTRU of claim 11 wherein the transmitted status report indicates anegative acknowledgement (NACK) if other RLC PDUs are missing in areordering buffer with a SN smaller than the SN of a next expected RLCPDU.